1. Field of the Invention
The invention relates to a shaking unit and to a method for pneumatic excitation of a shaking unit.
2. Description of the Related Art
Shaking units and excitation methods are known for example from EP 0 635 601 A1, WO 2009/138491 A1 and U.S. Pat. No. 5,759,354. Here, a machine part mass, namely a roll in a paper machine such as a breast roll in a paper machine is excited by way of a shaking unit into one-dimensional oscillating movements parallel to the roll axis. The shaking unit includes a coupling part for mechanical coupling to the machine part mass, whereby EP 0 635 601 A1 and WO 2009/138491 A1 also disclose a counter mass which is coupled resiliently by the coupling part to the machine part mass. The resilient coupling in the arrangement according to WO 2009/138491 A1 is a hydraulic cylinder-piston unit, whereas EP 0 635 601 A1 utilizes a piston-cylinder unit for this function having springs arranged in piston displacements with the assistance of pneumatic springs formed by the piston displacements and a suitable filling gas within the piston displacements. EP 0 635 601 A1 additionally features an auxiliary piston which can be controlled pneumatically in order to cause a suitable oscillation in the desired manner. The arrangements in EP 0 635 601 A1 and WO 2009/138491 A1 have in common that the counter mass must have a relatively high weight and be able to freely oscillate while at the same time supporting a cylinder in which a piston moves back and forth and which is connected rigidly in the oscillation direction with the machine part mass, in other words with the respective roll.
What is needed in the art is a shaking unit of this type or respectively an excitation method of this type which is less complex.